Tuesday, February 22, 2011

Eagle Stalking--Successes and Mistakes

If you want to earn your photography merit badge in this part of Wisconsin you must show eagle pictures taken at Prairie du Sac in your portfolio. There is a power dam across the Wisconsin River there that, among other things, creates Wisconsin's mini challenge to Lake Meade. It also keeps the river ice free downstream. So when other lakes and rivers freeze over the eagles gather.

There were at least 20 eagles in view on the stretch of river where we stopped. This was at the official viewing platform on the bluff in the center of the river town. Further up Highway 87 there are two other sites, the VFW park down by the edge of the river and the dam parking lot. When we checked them out there were no eagles.

We thought the half dozen boats with fishermen frightened the eagles off but latter we  were told that because of the unusual February snow melt  more water than usual was flowing down the dam's spillway. So the sandbars where the eagles stopped to digest their catch were under water.

I shared the platform with two other photographers.  On my right was an older man from Milwaukee. For the last five years he and a friend had been making the trip to Prairie du Sac to see for eagles. In previous years they hadn't seen a single bird. This year they had  this flock to photograph. Unfortunately he had brought only one roll of film for his little plastic 1990's point and shoot. A photographic opportunity lost for ever.

On my left was a much young photographer with a full frame Canon and matching big lens. When I commented that he certainly had brought the right equipment, he snorted and answered "Hardly." He had only brought along a 300mm f2.8 lens with it's matching 2X teleconverter.

As for me, I had my Nikon D700. But mounted on it was my Promaster 75-300mm f4.5-5.6 zoom lens.  In more ways than one I was the man in the middle.

Once I had my images on my computer I checked out the Canon lens-- a bargain at Amazon for a mere $3400.  So unless I win the lottery, I'm not about to run out and buy the Nikon Version

I paid  $15 for my used Promaster--according to the EXIF info a re-branded Sigma APO macro (4/1) lens-- and will be sticking with it. According to the reviews it isn't outstanding, but gives good value for the money.

If you use it right. Something  I know I was not doing. So after poking around the Internet and seeing how other D7000 bird photographer do it, I set up a user mode:

Shutter 1/1200,  aperture f11 and ISO auto with an upper limit of 6400.  The speed should freeze birds in flight and eliminate camera shake since the lens is not image stabilized.  The f# give good DOF and is 2 stops down at the lens' sweet spot.  The variable ISO is the independent variable that sets the exposure. On a bright sunny day the ISO end up at about 600.

For focusing I set the camera to 39 focusing points using the 3D continuous mode. In Nikon talk 3D means the camera stores color information about the bird to keep it in focus.

Let you know how these settings work out.

And the answer is

Taken with a few minor changes.  The shutter speed was 1/2000 sec and because the sky had clouded over the ISO had moved up to 2200.  Still usable but I think I could have opened the iris a stop without a problem. The big difference was in the focusing with a far bigger percentage of images spot on than before.

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